The present invention is directed to ultracentrifuge tubes and, more particularly, is directed to a multi-chamber ultracentrifuge tube.
One of the more important areas in medical research is directed to an understanding of the causes of heart attacks and strokes as the result of arteriosclerosis. Incalculable studies over many years have revealed that one of the primary causes of death or incapacitation in adults over their mid-thirties is attributable to heart attacks as well as strokes. Heart disease has reached epidemic proportion in modern civilization.
One of the important research studies being conducted in the medical field is to learn not only how to prevent the occurrence of heart attacks, but also how to predict the likelihood of a heart attack occurring for a particular individual. Such predictions will allow the patient to undergo a program to avoid the occurrence of heart attack. Large research studies have found that the quantitation of cholesterol in each of the lipoprotein density classes provides patient information that is extremely helpful in predicting the risk of coronary heart disease. The lipoproteins in the blood are classified by their buoyant density. It is generally well known that the relative magnitudes of density for the various lipoproteins can be classified as follows: very low density lipoproteins (VLDL), 0.95 to 1.006 grams per ml; low density lipoproteins (LDL), 1.006 to 1.063 grams per ml; and high density lipoproteins (HDL), 1.063 to 1.21 grams per ml.
In view of the relative gradations of density between the various lipoproteins, centrifugation provides an obvious choice to accomplish the separation of the various lipoproteins from each other under a high centrifugal force field. Therefore, lipoprotein investigation involves the utilization of a preparative ultracentrifuge after which the separated lipoproteins are subjected to analytical measurements to determine the cholesterol concentration. Since the sample is normally placed in a typical single chamber centrifuge tube for insertion in a fixed angle or vertical tube ultracentrifuge rotor, the separate bands formed during centrifugation will reorient after the centrifugation is completed. Some residue from one band may be left on the tube wall and contact other bands as they reorient to a new position affecting the purity of the separation. One type of single chamber tube used is that which is disclosed in U.S. Pat. No. 4,301,963 issued to Steven T. Nielsen on Nov. 24, 1981 and entitled "Integral One Piece Centrifuge Tube."
After centrifugation each separated lipoprotein fraction must be physically isolated so that it is not contaminated and will not result in an incorrect reading of the cholesterol concentration for that particular density lipoprotein. Typical techniques utilized to accomplish this separation are centrifuge tube slicing or aspiration. In the tube slicing technique the cutting blade must be carefully positioned and be maintained in an extremely clean condition. Furthermore, depending upon the particular type of tube utilized, a significant amount of force may have to be applied by the user to pierce the tube. Once the tube is sliced, the upper portion of the tube is isolated and the separated lipoprotein can be aspirated out of the sliced-off portion of the tube without disturbing the other separated lipoprotein bands in the remainder of the tube.
In the straight aspiration technique, bands are pipetted or suctioned off layer by layer. This operation may be simple and relatively convenient, but it poses a strong possibility of contamination. This is because lipoproteins from the removed fraction may adhere to the side of the tube and contaminate the remaining fraction.
The need exists in the process of measuring the cholesterol concentration in lipoprotein separations for a means to conveniently isolate the separated lipoproteins so that the subsequent investigation of cholesterol concentration in the separated lipoproteins can be accomplished with a minimum of effort and a minimum of contamination.